In general, a photolithography process has been used for forming fine patterns in the fields of the related art, such as those of displays and semiconductors. However, because the formation of fine patterns using the photolithography process is performed through operations of photoresist coating-exposing-developing-etching-stripping, the process is generally complex, raw materials such as photoresist, etc. are consumed in large amounts, and liquid waste is generated in the developing and etching processes to thereby incur costs associated with the treatment of liquid waste.
Accordingly, to overcome these problems, methods for forming fine patterns using printing techniques other than the photolithography process have recently been developed. When fine patterns are manufactured using printing techniques, it is advantageous that the process be simple, the consumption of raw materials minimized, and the generation of liquid waste eliminated so as to lower manufacturing costs.
These methods of forming fine patterns using printing techniques have been applied to the formation of a color filter, an electromagnetic shielding (EMI) filter, a thin-film transistor (TFT) wiring and a micro pattern substrate.
Printing methods enabling the formation of fine patterns include gravure printing, offset printing, screen printing, and the like may be used therefor. Among these, offset printing is especially useful because relatively fine printing patterns may be formed to have a uniform thickness.
Offset printing is a method of printing a pattern by applying paste, such as ink, to a groove formed in a pattern of a cliche for offset printing such that the groove is filled therewith, removing the extra paste applied to areas other than the groove using a doctor blade, transcribing the paste filled in the groove to a silicon blanket (removal process), and transcribing the paste already transcribed on the silicon blanket to a subject to be printed (setting process).
A cliche for offset printing is formed by a method of etching a metal substrate to form grooves or by a method of etching a special glass substrate. For example, a thin layer of a material such as chrome is formed on a glass substrate, a photosensitive resin is applied thereto and then, areas in which grooves are to be formed are exposed to a laser beam or the like. Subsequently, the photosensitive resin of the exposed area is removed through a developing process to expose the chrome layer in the areas in which grooves are to be formed and then, the chrome in the exposed areas may be removed by the etching thereof to expose glass, which may be re-etched with a fluoride solution to manufacture a cliche for offset printing with grooves having an appropriate width and depth. However, when a glass substrate is used as a cliche for offset printing, the surface thereof may be easily damaged by being scraped with a doctor blade. In order to solve this, methods of improving the surface strength of a glass substrate by treating the surface of the glass substrate with hybrid nickel or a diamond like coating (DLC) have been recently developed.
Fine patterns may be formed by a simple method of filling a cliche for offset printing manufactured as above, in which a desired pattern is intagliated, with a paste. The method of offset printing is advantageous in that the processes there of are simpler and the manufacturing costs thereof are lower as compared to those of the related art photolithography. However, when a pattern to be printed has a plurality of intersection units, a line width reduction, which is undesirable, may be generated around the intersection units during printing pattern formation using an offset printing method. FIG. 1 is a photograph illustrating a printed mesh pattern using a cliche for offset printing of the related art. As shown in FIG. 1, it can be seen that line width reduction around the intersection units is generated when a mesh pattern is formed using a cliche for offset printing of the related art. Because depressions are generated around the intersection units during the process of scraping the paste applied to the surface of a printing substrate with a doctor blade, the phenomenon of line width reduction may occur. These depression phenomena cause the line width around the intersection units to be reduced, and disconnection may occur when the phenomena are severe. Therefore, when a wiring board has many intersection units or a mesh pattern of an electromagnetic shielding filter printed thereon, it is disadvantageous that the line width around the intersection units be reduced as the resistance properties of a product may be deteriorated by disconnection.
Although the deterioration of resistance properties may be solved to some degree by increasing the line width, permeability may be reduced by an increase in line width, thereby lowering the brightness of a display device.